The overall goal of this proposal is to support the continuing development of the applicant as a scientist studying generalized social phobia (GSP) (also known as generalized social anxiety disorder), related traits, behaviors and disorders. The applicant will develop his capacity to utilize brain imaging methods in close collaboration with imaging experts, in order to assess brain function associated with these conditions. Training goalsfocus on increasing the applicant's understanding of single photon computerized tomography (SPECT) and positron emission tomography (PET) techniques and dopamine (DA) neurociruitry. A research goal is to integrate multiple imaging findings in GSP and related conditions, toward testing models of DA neurocircuitry. This program builds on recent findings of low DAD2 receptor and DA transporter binding in GSP and the related trait of detachment. The applicant will further characterize DA system dysfunction in collaboration with N.Y. State Psychiatric Institute's Functional Brain Mapping Division, directed by Dr. Marc Laruelle. The applicant will use PET and SPECT to study the relationship of D2 receptors, DA transporters, and DA release in patients with GSP (specific aim 1). Main hypotheses are that striatal D2 receptor and DA transporter binding will be low, and DA release will be blunted. Specific aim 2 will test whether DA system findings in GSP represent a trait or a state finding that changes with treatment. Hypotheses are that low D2 binding at baseline and change in D2 binding during treatment will be associated with symptomatic improvement during treatment Specficity offindings to GSP will be studied by assessing D2 receptor binding and amphetamine-induced DA release in patients with major depressive disorder with atypical features, which like GSP is characterized by interpersonal sensitivity, (specific aim 3). Specific aim 4 will study associations of biologically salient traits of detachment, submissive behavior, capacity for social reward, and social memory with GSP and DA function. Long-term goals include integration of phenomenology related to GSP with imaging measures, treatment outcome, animal findings, and genetics. Better understanding of the neurocircuitry associated with GSP holds promise for improving diagnosis and treatment strategies.